Dimmable LED light unit and method of replacing a light unit

Abstract

A dimmable LED light unit, in particular for a passenger transportation vehicle, such as an aircraft, a road vehicle, a ship or a rail car, is disclosed that comprises a power input adapted to receive electrical power from a power source, at least one LED, and an LED drive and control module coupled between the power input and the at least one LED, wherein the LED drive and control module is adapted to receive an LED control signal indicative of a desired light intensity of the dimmable LED light unit.

The invention claimed is: 
     
       1. An aircraft interior lighting system, comprising:
 an on-board AC electricity distribution network; and 
 at least one dimmable interior aircraft LED light unit comprising:
 a power input adapted to receive electrical power from a power source, 
 at least one LED, and 
 an LED drive and control module coupled between the power input and the at least one LED, wherein the LED drive and control module is adapted to receive an LED control signal indicative of a desired light intensity of the dimmable LED light unit, 
 
 wherein the LED drive and control module is configured to provide a drive current to the at least one LED resulting in the desired light intensity of the dimmable LED light unit, the drive current having a drive current amplitude and a drive current duty cycle, wherein the LED drive and control module is configured to set the drive current amplitude within an amplitude range and to set the drive current duty cycle within a duty cycle range in response to the LED control signal; 
 wherein the LED drive and control module is configured to set the drive current duty cycle to 100% and to variably set the drive current amplitude within the amplitude range, when the desired light intensity is above a first light intensity threshold value (In Th,1 ), and 
 wherein the power input is an AC power input connected to the on-board AC electricity distribution network and adapted to receive electrical power from the on-board AC electricity distribution network, and 
 wherein the on-board electricity distribution network provides a voltage of 115 V and operates at a frequency of 400 Hz; 
 wherein the dimmable interior aircraft LED light unit further comprises a power factor correction circuit coupled between the AC power input and the LED drive and control module, the power factor correction circuit comprising a buffer capacitor, wherein the buffer capacitor of the power factor correction circuit is smaller than 75 μF; 
 wherein the at least one dimmable interior aircraft LED light unit comprises at least one of an aircraft cabin general illumination light unit and a wash cabin illumination light unit. 
 
     
     
       2. An aircraft interior lighting system according to  claim 1 , wherein the first light intensity threshold value (In Th,1 ) is between 15% and 50% of a maximum light intensity. 
     
     
       3. An aircraft interior lighting system according to  claim 1 , wherein the LED drive and control module of the dimmable interior aircraft LED light unit is configured to set the drive current amplitude according to a linear relationship with the desired light intensity, when the desired light intensity is above the first light intensity threshold value (In Th,1 ). 
     
     
       4. An aircraft interior lighting system according to  claim 1 , wherein the LED drive and control module of the dimmable interior aircraft LED light unit is configured to set the drive current amplitude to a minimum current amplitude value (I Min ) and to variably set the drive current duty cycle within the duty cycle range, when the desired light intensity is below a second light intensity threshold value (In Th,2 ). 
     
     
       5. An aircraft interior lighting system according to  claim 4 , wherein the second light intensity threshold value (In Th,2 ) is between 15% and 50% of the maximum light intensity. 
     
     
       6. An aircraft interior lighting system according to  claim 4 , wherein the LED drive and control module of the dimmable interior aircraft LED light unit is configured to set the drive current duty cycle according to a linear relationship with the desired light intensity, when the desired light intensity is below the second light intensity threshold value (In Th,2 ). 
     
     
       7. An aircraft interior lighting system according to  claim 4 , wherein the first light intensity threshold value (In Th,1 ) is equal to the second light intensity threshold value (In Th,2 ). 
     
     
       8. An aircraft interior lighting system according to  claim 4 , wherein the second light intensity threshold value (In Th,2 ) is between 20% and 30% of the maximum light intensity. 
     
     
       9. An aircraft interior lighting system according to  claim 4 , wherein the second light intensity threshold value (In Th,2 ) is at about 25% of the maximum light intensity. 
     
     
       10. An aircraft interior lighting system according to  claim 1 , wherein the LED drive and control module of the dimmable interior aircraft LED light unit comprises:
 a controller configured to receive the LED control signal and to provide an amplitude control signal indicative of the drive current amplitude and a duty cycle control signal indicative of the drive current duty cycle, and 
 an LED driver configured to receive the amplitude control signal and the duty cycle control signal and configured to provide the drive current to the at least one LED ( 4 ) as a response to receiving the amplitude control signal and the duty cycle control signal. 
 
     
     
       11. An aircraft interior lighting system according to  claim 1 , wherein the power factor correction circuit of the dimmable interior aircraft LED light unit is adapted to receive AC power with an AC voltage of between 100 V and 150 V and with an AC current of between 150 mA and 300 mA. 
     
     
       12. An aircraft interior lighting system according to  claim 1 , wherein the at least one LED of the dimmable interior aircraft LED light unit is a chain of a plurality of LED's. 
     
     
       13. An aircraft having the aircraft interior lighting system of  claim 1 , with the at least one dimmable interior aircraft LED light unit being positioned in an interior of the aircraft. 
     
     
       14. An aircraft interior lighting system according to  claim 1 , wherein the first light intensity threshold value (In Th,1 ) is between 20% and 30% of the maximum light intensity. 
     
     
       15. An aircraft interior lighting system according to  claim 1 , wherein the first light intensity threshold value (In Th,1 ) is at about 25% of the maximum light intensity. 
     
     
       16. An aircraft interior lighting system according to  claim 1 , wherein the power factor correction circuit is adapted to receive AC power with an AC voltage of between 100 V and 150 V and with an AC current of between 150 mA and 300 mA and wherein the buffer capacitor of the power factor correction circuit is smaller than 50 μF. 
     
     
       17. Method of replacing a used light unit in an aircraft interior lighting system with a dimmable LED interior aircraft light unit according to  claim 1 , the method comprising the steps of:
 disconnecting the used light unit from the on-board electricity distribution network; and 
 connecting the power input of the dimmable LED interior aircraft light unit according to  claim 1  to the on-board electricity distribution network.